ML20127B913

Summary of Util 921130 IPE Rept in Accordance W/Generic Ltr 88-20, IPE for Severe Accident Vulnerabilities

ML20127B913
Person / Time
Site:	Duane Arnold
Issue date:	01/08/1993
From:	Pulsifer R Office of Nuclear Reactor Regulation
To:	Hannon J Office of Nuclear Reactor Regulation
References
GL-88-20, TAC-M74407, NUDOCS 9301130197
Download: ML20127B913 (2)

Text

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%....+/ i January 8, 1993 l Docket No. 50-331 MEMORANDUM FOR: John N. Hannon, Director Project Directorate 111-3 ,

Division of Reactor Projects lil/IV/V j FROM: Robert M. Pulsifer, Project Manager Project Directorate 111-3  :

Division of Reactor Projects Ill/IV/V i

SUMMARY

OF DUANE ARNOLD ENERGY CENTER IPE (TAC NO M74407)

The Iowa Electric Light and Power Company (IELP) submitted its Individual Plant Examination (IPE) report for the Duane Arnold Energy Center (DAEC) on November 30, 1992, in accordance with Generic Letter 88-20, " Individual Plant Examination for Severe Accident vulnerabilities." The DAEC IPE effort consists of both a Level 1 and a Level 2 Probabilistic Risk Assessment (PRA).

The objectives of this IPE were to gain a more quantitative understanding of the overall probabilities of core damage and fission product releases and to understand the most likely severe accident sequences. DAEC also wanted the system knowledge gained to be retained by in-house engineering personnel and to have aspects of the IPE study that were supported by external consultants performed in a manner to maximize technology transfer to IELP. The IPE reflects the design and operation of DAEC as of startup from the April 1992 refueling outage with credit added for the Hardened Wetwell Vent which was scheduled and completed by December 31, 1992, it was concluded that DAEC is a plant with a low risk of core damage and fission product release. The Level 1 analysis resulted in a Core Damage frequency (CDf) of 7.84E-6 per reactor year. Five sequences were identified as contributing at least 5% of the CDF and these sequences contributed 3.4E-6 per reactor year of the total. It has one sequence that just meets the IE-6 screening criteria while all others were less. This one sequence represents the loss of all 125 Volt DC power to a common cause failure of both station batteries or 13% of CDF. The other four sequences are: (1) Loss of Decay Heat Removal (10% CDF), (2) ATWS with failure of Standby Liquid Control (9% CDF),

(3) Station Blackout for greater than 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> (7% CDF), and (4) Loss of Offsite Power with early HPCl/RCIC failure (5% CDF).

Based on the results of its IPE, DAEC has identified no specific vulnerabilities of the plant to severe accidents. It has also identified no specific ;mprovements to either hardware or procedures which are necessary because of this study. Of the outstanding USIs or GSIs, DAEC has chosen only

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John N. Hannon January 8, 1993  !

l USI A-45, " Shutdown Decay Heat Removal Requirements," to be resolved as part I of the IPE effort. There were, however, several insights obtained during the development of the IPE which will be evaluated by DAEC.

Of all the plants listed in NUREG-ll50 the licensee reviewed information regarding Peach Bottom, because it most closely resembles DAEC. Several insights were listed where one was that common cause failures contribute significantly to risk. Common cause failures of the station batteries and the diesel generators were the most significant events.

The DAEC reliabilit; avaluation indicates that the containment has a high reliability although the results are affected by any reduction in containment isolat:on reliability. There is no additional accident management insight .

regardit.1 improvements in the DAEC Mark I containment isolation from the IPE.

IEPL is a ,,articipant in the industry efforts to develop severe accident management strategies and guidelines, it plans to implement these at DAEC when they become available as part of their overall severe accident process, including IPEEE.

ORIGINAI, SIGNED llY:

Robert M. Pulsifer, Project Manager .

Project Directorate !!I-3 Division of Reactor Projects Ill/IV/V DISTRIBUTION Docket File WBeckner NRC & Local PDRs DWheeler PD3-3 Reading JFlack, RES TMurley/fMiraglia RHernan JPartlow ACRS (10)

WRussell 0GC JRoe EJordan JZwolinski JHannon TKing PKreutzer AThadani RPulsifer JRichardson Region Ill, DRP RBarrett 0FFICE PDill-3:LA:DRPW PDill-3:PM:DRPW, _

NAME PKreutzer m d . RMPulsifer/rm[fhkf DATE ) / $ /9id h e ///93 0FFICIAL RECORD DOCUMENT NAME: G:\DUANEARN\lPEMTSUY.MTS